This invention relates to a drive bearing arrangement for a watercraft, and more particularly to an improved arrangement for journaling a shaft and providing a driving coupling between it and a coupling element.
In many forms of watercraft, a shaft is provided which is journaled within the inner race of a bearing and which is coupled to another shaft by means of a flexible coupling. For example, in many types of watercraft, the propeller shaft, which is connected to a propulsion device such as a propeller in a propeller driven watercraft or the impeller of a jet pump in a jet propelled watercraft is journalled at its forward end within an anti-friction bearing. The forward end of this propeller shaft is coupled by means of a coupling to the engine output shaft.
Normally the propeller shaft is drivingly connected to a coupling element by means of a tubular sleeve that has a splined connection at one end to the propeller shaft and a splined connection at the other end to the coupling element. This tubular sleeve is press-fit within the inner race of a supporting bearing. Normally the sleeve is formed from a corrosion-resistant material such as stainless steel or the like.
Because of this type of connection, the actual splines that transmit the power are relatively small and this can give rise to low capability of power transmission and/or the likelihood of premature wear. The problems can be alleviated by providing a larger diameter for the tubular member, but because of the spacial requirements this is not always possible. In addition, the tubular member could be formed from a higher strength material, but the its corrosion-resistant properties would be lost and the seals which are engaged with the tubular member on the opposite sides of the anti-friction bearing would be subject to premature wear.
The problems with the prior art-type of construction can be understood by reference to FIG. 1, which is a side elevational view with portions broken away, showing the connection of the front end of a propeller shaft to a coupling element of a flexible coupling which is driven by an engine. The propeller shaft, indicated by the reference number 11, is journaled within a bearing assembly 12 that is affixed to the front of a bulkhead through which the propeller shaft 11 passes. The bearing assembly 12 includes a plurality of anti-friction balls 13 that are received within an inner race 14.
A tubular sleeve 15, formed from a corrosion-resistant material such as stainless steel, is press-fit into the inner race 14 and has internal splines 16 which are engaged with external splines 17 formed at the forward end of the propeller shaft 11.
The forward end of the tubular member 15 is provided with external splines 18 that are received in internal splines of a hub 19 of a coupling element, indicated generally by the reference number 21 and shown in phantom in this figure. The coupling element 21 forms one part of a conventional vibration damping coupling which is coupled in a known matter to the engine output shaft for driving the propeller shaft 11.
A pair of seals 22 are disposed on opposite sides of the bearing elements 13 and are engaged with the outer periphery of the tubular member 15.
It should be readily apparent that the splines 18 are relatively small and hence the power transmitting capabilities of the arrangement are reduced, and the likelihood of wear increased. As previously noted, it is not always feasible to increase the diameter of the sleeve 15 so as to provide a higher strength assembly. In addition, if stronger materials are used to form the sleeve 15, then the corrosion-resistant properties will be lost and the seals 22 could be damaged when the sleeve 15 becomes corroded.
It is, therefore, a principal object of this invention to provide an improved coupling arrangement for connecting a shaft to a coupling element.
It is a further object of this invention to provide an improved, high-strength and corrosion-resistant coupling between a coupling element and a shaft of a marine propulsion unit.